Valve for an aerosol device

ABSTRACT

A valve for an aerosol device includes a valve assembly receivable in an opening provided in a container of the aerosol device to close the opening and includes a seal between the valve assembly and the container.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve for an aerosol device, and morespecifically, but not exclusively, to a valve for an aerosol device fora metered dose inhaler.

2. The Prior Art

The term aerosol is considered to encompass all types of pressurizedcontainers used for delivery of aerosolized products meant for a varietyof medical and non-medical applications including, but not limited to,drugs, cosmetics (deodorants, hair sprays, hair mousses, shavingcreams), perfumes, air fresheners, insect repellents, cleaning agents,paints, lubricants and the like. Aerosol devices may deliveraerosolized, ingredients in an uneven or continuous manner deliveringvarying quantities per actuation, or in a uniform manner, deliveringpredetermined identical quantities, or doses, per actuation.

A metered dose inhaler is a dispenser designed to deliver a specificdose of medication to a user with each usage.

Typically, aerosol devices comprise a container and a valve crimped onthe container. The valve is fitted to the body of the container bycrimping a valve ferrule against the body of the container with anintermediate seal made of an elastomeric material compressed between thebody and the ferrule. The process of positioning a valve in place andcrimping around it to form a seal and close the container is timeconsuming. Aerosol devices produced in this way are prone to leakagesresulting from improper sealing of the valve and the body of thecontainer. Aside from the difficulty in obtaining an efficient seal, thestep of crimping involves a considerable amount of production timeduring the manufacture of such devices. Frequent testing of the devicesmust be conducted throughout the manufacturing process to ensure thatleaks are not present. This all requires extra skilled man-power andmachinery, thereby increasing the overall cost and time required for theproduction.

The problem of leaks is especially significant in the case of medicinalaerosol formulations. In medicinal aerosol formulations it is importantto ensure that an appropriate concentration of the drug in the containeris maintained throughout the entire usage period. Leakage of thepropellants in such devices can lead to non-uniform and unpredictabledrug delivery, which is a serious problem with these devices.

It is common in many aerosol devices to use thermoplastic elastomers asan additional means to obtain a more effective seal. However, inaerosols meant for medicinal purposes this technique has, furtherdrawbacks. Contact of the medication with an elastomer greatly increasesthe chances of drug contamination through the process of leaching. Ifthe elastomeric elements are not incorporated, in an effort to avoidthis problem, the sealing of the aerosol device through crimping iscompromised, leading to increased leakage problems as discussed above.

Numerous attempts have been made to make leakage resistant aerosoldevices. Various known aerosol devices incorporate an intermediate seal,either in the form of a ferrule gasket placed and compressed between thetop edge of the body of the container and the opposing surface of theferrule gasket, or of an O-ring placed around the exterior of the bodyof the container and compressed between the body of the container and anannular flange of the valve ferrule. Other approaches includeincorporating gaskets made up of material of varying durometer values,in an attempt to achieve more effective sealing. However, the problemsdiscussed above still remain.

It would be beneficial if a valve assembly could be provided for anaerosol device which enabled the aerosol device to be more easilysealed, while also allowing more efficient production of the aerosoldevice.

Conventional aerosol devices have a number of further disadvantages. Inmany cases, due to the shape of the container used, it is not possiblefor the container to dispense every last drop of a substance to bedelivered. This is wasteful in all applications, but is most significantwhere a medicament is to be delivered by the aerosol device. Canistersfor use with metered dose inhalers are designed to deliver a certainnumber of controlled doses of medicament to a user. The devices arecommonly employed in inhaler apparatus to treat asthma and similarcomplaints. Since in existing canisters there is often a quantity of themedicament which cannot be delivered, the container is routinelyover-filled (in some cases by up to fifteen percent). This not onlyincreases the amount of medicament, propellant and the size of containerrequired for a given number of doses, but also complicates thecalculation of the amount of medicament required. If one could be sureof complete exhaustion of a container during use, then less medicamentcould be used with a smaller container, the filling of which would besimplified because only the number of doses and size of each dose wouldneed to be known in order to determine the size/volume of containerrequired.

It is an object of the present invention to provide a valve for anaerosol device which also serves as a closure for the aerosol device. Itis a related object of the present invention to provide a valve assemblyfor an aerosol device which allows for nearly complete exhaustion of thesubstance contained in the aerosol device.

SUMMARY OF THE INVENTION

According to the present invention there is provided a valve assemblyfor an aerosol device, the valve assembly being receivable in an openingprovided in a container of the aerosol device to close said opening,wherein means are provided on the valve assembly to form a seal betweenthe valve assembly and a container.

The valve assembly is preferably substantially cylindrical, so as to belocatable in an open end of a substantially cylindrical container.Peripheral sealing means may then be provided around the entireperiphery of the valve assembly, to provide a seal between the outsideof the valve assembly and the inside of the container. Peripheralsealing of this type is preferable to so called ‘face sealing’, wherethe valve member is sealed only against a planar face of a canister. Abetter seal can be achieved from the periphery of a valve assembly thanfrom simple interaction of two substantially planar surfaces. Facesealing typically also requires crimping of a ferrule with a gasket anda valve, which can cause damage to the neck of the can. The valveassembly can be held in place by a cap, positioned around and crimped orotherwise attached to the outside of the container. Due to the valveassembly closing the entire opening of the container, and due to theperipheral sealing, there is no need for the means of attaching the capmember to also serve as a seal. This results in an aerosol device whichis more simply and efficiently manufactured.

Peripheral sealing is most easily achieved in an assembly where thecontainer and valve assembly are both cylindrical in shape. Sealingelements such as elastomeric rings may be employed to achieve the sealbetween an exterior part of the valve element and an interior part ofthe container.

The valve assembly preferably has a flat portion, perhaps formed by abody part of the valve assembly, which, in use, faces towards theinterior of a container. The flat end portion minimises the chances of asubstance forming pools (ullage) or otherwise being prevented from beingexpelled from the container. To maximise the chances of expelling everydrop of a substance, channels or suitable apertures should be providedon or immediately adjacent the flat surface to provide access to theinterior of the valve assembly.

The component parts of the valve assembly may be arranged in a valvebody and contained therein by a sealing piece, which may be snap-fittogether, or joined together by other suitable means. This provides aself contained valve assembly ready for insertion into a suitablecontainer. The component parts of the valve assembly may comprise, amongothers, a valve stem, a spring and a valve chamber. A space ispreferably provided between the valve stem and valve chamber, to containa volume of substance comprising one ‘dose’ for delivery when the valveis activated.

The component parts of the valve assembly may further comprise a seatgasket positioned between the valve chamber and the sealing piece. Theseat gasket preferably surrounds the valve stem and is capable ofsealing an aperture provided in the valve stem. The valve stem ispreferably movable, for example slidable, within the valve chamber. Byrestricting the movement of the seat gasket, the aperture in the valvestem can be sealed and unsealed as the valve stern moves within thevalve chamber.

The valve assembly is particularly suitable for application to aerosoldevices containing medicament to be delivered to a patient, for examplein the form of MDI canisters.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention will be better understood with reference to thefollowing detailed description of a preferred embodiment. The detaileddescription is included by way of example only, and is not intended tolimit the protection sought. Throughout the detailed descriptionreference is made to the accompanying drawings, in which:

FIG. 1 is a perspective view of a valve body from a valve assembly of anaerosol device according to a first embodiment of the present invention;

FIG. 2 is a perspective view of a valve chamber from the valve assemblyof said device according to a first embodiment of the present invention;

FIG. 3 is a perspective view of a valve stem from a valve assembly ofsaid device according to a first embodiment of the present invention;

FIG. 4 is a perspective view of a sealing piece from a valve assembly ofsaid device according to a first embodiment of the present invention;

FIG. 5 is an exploded view of a valve assembly of said device accordingto a first embodiment of the present invention, including the partsshown in FIGS. 1-4;

FIG. 6 is a perspective view of a container of said device according toa first embodiment of the present invention;

FIG. 7 is a perspective view of an end cap of said device according to afirst embodiment of the present invention; and

FIG. 8 is an exploded view of said aerosol device according to a firstembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The valve body 2 of FIG. 1 comprises an open hollow tubular section 4 atone end, and an enclosed tubular section 6, of a smaller diameter, atthe other. On the interior of the valve body 2, the tubular sections 4,6join up such that the valve body 2 is substantially hollow. Between thetwo tubular sections 4,6, to the exterior of the valve body 2, acircular disc shaped flange 8 is provided. On the side of the flange 8adjacent the closed tubular section, a raised area 10 is provided, withtwo apertures 12 on opposite sides thereof.

The apertures 12 are in the form of slots which run against the flatsurface of the flange 8 and provide fluid communication between theoutside and the inside of the valve body 2. A circumferential ridge 14is provided to the exterior of the open tubular section 4 of the valvebody 2.

FIG. 2 shows a valve chamber 16 which, in use, fits inside the opentubular section 4 of the valve body 2 of FIG. 1. The valve chamber 16has a main cylindrical section 18 with an external diametersubstantially equal to the internal diameter of the open tubular section4 of the valve body 2. At one end of the cylindrical section 18 there isa circular flange 20 which is sized to rest on a lip provided on theinterior of the open tubular section 4 of the valve body 2, adjacent theopen end. Accordingly, the flat end section 22 of the flange 20 finishesflush with the open end of the open tubular section 4 of the valve body2 when the valve body 2 and valve chamber 16 are assembled.

At the end of the cylindrical section 18 opposite the flange 20, asquare shoulder 24 is provided. Radially inward from the squareshoulder, a truncated cone section 26 narrows the outer diameter of oneend of the valve chamber 16 to a circular opening 28 which leads to anaxial tubular bore 30 running through the centre of the valve chamber16, emerging at the centre of the flange 20. The opening 28 at the endof the valve chamber 16 is of a smaller diameter than the bore 30 whichruns through the valve chamber 16, and out of the centre of the flange20.

FIG. 3 shows a preferred valve stem 32 which, in use, is positioned inthe bore 30 of the valve chamber 16. The valve stem 32 is essentially athin tubular part, with one end enclosed. The open end 34 of the tube isthe part of the valve assembly through which a substance is expelledduring use. The closed end 36 of the tube is opposite to the open end34, and is of a smaller diameter. Four radially extending fins 38 areprovided on a part of the closed end 36 of the valve stem 32, spacedslightly from the end. The fins 38 give an effective external diameterlarger than the closed end 36 of the valve stem 32, but slightly smallerthan its main hollow section. A flange 40 is provided approximately halfway along the valve stem 32. To the side of the flange 40 adjacent theopen end 34 of the valve stem 32 there is a small aperture 42. Theaperture 42 provides fluid communication with the hollow section of thevalve stem 32.

The external diameter of the hollow part of the valve stem 32 isslightly smaller than that of the opening 28 at the end of the valvechamber 16 adjacent the truncated cone section 26. However, the diameterof the flange 40 is slightly larger than the opening 28 at the end ofthe valve chamber 16, but slightly smaller than the internal diameter ofthe bore 30 which runs through the valve chamber 16. The significance ofthis will be explained below.

The sealing piece 44 shown in FIG. 4 comprises a section of tube 46which is largely closed at one end. In use, it fits over the open hollowtubular section 4 of the valve body 2. The internal diameter of thesealing piece 44 is substantially the same as the external diameter ofthe open hollow tubular section 4 of the valve body 2, to ensure aslight interference fit therebetween. The interior surface (not shown)of the sealing piece 44 further comprises a circumferential channel toengage with the circumferential ridge 14 of the valve body 2. Twofurther circumferential channels 48 are provided on the outside wall 46of the sealing piece 44 to accommodate elastomeric sealing rings (notshown). The largely closed end of the sealing piece 44 is provided as aflat disc-like end 50 having a small circular hole 52 in the centre. Thesmall hole 52 is just large enough for the hollow part of the valve stem32 to pass through.

The interaction of the various parts of the valve assembly described inFIGS. 1-4 will now be described in relation to the exploded view of FIG.5.

FIG. 5 shows a front view of the various components that make up a valveassembly 60 in accordance with the present invention. Along with thevalve body 2, valve chamber 16, valve stem 32 and sealing piece 44described previously, the assembly further comprises a spring 54, a seatgasket 56 and two elastomeric sealing rings 58. For the sake ofsimplicity in the drawings, the reference numbers for various individualparts of the components shown in FIG. 5 are not shown on the explodedview. The reader is referred back to FIGS. 1-4.

The assembly of the valve assembly 60 is relatively straightforward. Thespring 54 is inserted into the valve body 2 where it locates in theenclosed tubular section 6. The valve stem 32 is inserted into the valvechamber 16 so that the closed end 36 of the valve stem 32 passes throughthe opening 28 in the valve chamber 16. The seat gasket 56 is positionedon the valve stem 32 so that it abuts the flange 40. In this position,the seat gasket 56 covers the aperture 42 in the side of the valve stem32. The seat gasket has a stepped cross section, the smaller diameterpart 62 of which sits against the flange 40 on the valve stem 32, and issized so as to fit inside the bore 30 of the valve chamber. The largerdiameter part 64 rests on top of the flange 20 of the valve chamber 16.

The valve chamber 16, with the valve stem 32 and seat gasket 56 inplace, is then lowered into the valve body 2. The closed end 36 of thevalve stem 32 engages with the spring 54, which is supported against theradially extending fins 38 of the valve stem 32. Once the valve chamber16 has been pushed firmly into position inside the valve body 2, thesealing piece 44, with elastomeric sealing rings 58 in position in itsexternal circumferential channels 48, is pushed into place around theoutside of the valve body 2 such that the circumferential ridge 14 ofthe valve body 2 engages with the internal circumferential channel (notshown) of the sealing piece 44. The valve assembly 60 then forms acomplete self contained unit.

Because the hollow section of the valve stem 32 is of a slightly greaterdiameter than the effective diameter of the radially extending fins 38,the valve stem 32 tends to naturally sit in the valve chamber 16 suchthat only the closed end 36 of the valve stem 32 and the radiallyextending fins 38 extend beyond the opening 28 in the valve chamber 16.The hollow portion of the valve stem 32 is capable of passing throughthe opening 28, but due to its greater diameter some further impetus(force) is require to make it do so. The result of this is that, whenthe valve assembly 60 is in its complete state, a force applied to theopen end 34 of the valve stem must overcome not only the resistive forceof the spring 54, but also the additional resistance caused due to thechange in diameter of the valve stem 32. This provides a greater initialresistance than the spring 54 alone, which is helpful in avoidingaccidental actuation of the valve assembly 60. When the external forceis removed, the restoring force of the spring 54 is sufficient to returnthe valve stem 32 to its rest position. The flange portion 40 of thevalve stem 32 is too large to pass through the opening 28 in the valvechamber 16, and so provides a stop to avoid over actuation of the valvestem 32.

The container 66 shown in FIG. 6 is configured to receive the valveassembly 60 described above. The container 66 has a simple cylindricalshape and is enclosed at one end only. The open end 68 of the container66 is sized to receive the valve assembly 60. The internal diameter ofthe open end 68 is substantially the same as, or slightly smaller than,the external diameter of the complete valve assembly 60, including theelastomeric sealing rings 58. A lip (not shown) is provided on theinterior of the container 66 to support the valve assembly 60. The lipis positioned such that the flat disc like end 50 of the sealing piece44 of the valve assembly 60 is positioned flush with the opening of thecontainer 66 once assembled. A circumferential groove 70 is provided inthe outside wall of the container 66 adjacent the open end 68.

The metal end cap 72 shown in FIG. 7 is designed to be placed over theopen end 68 of the container 66 once the valve assembly 60 is in place,in order to form a complete aerosol device. The end cap 72 takes theform of a cylinder with one flat substantially closed end face with ahole 74 provided in the centre. The end cap 72 can be crimped orattached by some other means to the container 66. Where crimping isused, the forces involved can be much less than in typical aerosolmanufacture. This is because the end cap 72 of the present inventionneed not serve any sealing purpose, but merely has to retain the valveassembly 60 in position in the container 66. Furthermore, there is noneed to apply any crimping force directly to the valve assembly 60, sothe possibility of causing damage to the valve is minimised.

The final assembly of the aerosol device 76 will be understood withreference to FIG. 8. FIG. 8 shows front views of the container 66, theend cap 72 and the complete valve assembly 60.

The valve assembly 60 is inserted into the open end 68 of the container66, such that it rests on the internal lip (not shown) provided therein.The elastomeric sealing rings 58 of the valve assembly 60 form a sealaround the entire circumference of the valve assembly 60. The end cap 72is then placed over the end of the container 66 with the valve stem 32extending out through the hole 74, and crimped into the circumferentialgroove 70 provided on the container 66 to retain the valve assembly 60in place. If better joining is required then further elastomericelements may be incorporated between the end cap 72 and the container66. Alternatively, or additionally, one or more further circumferentialgrooves may be provided in the exterior surface of the container.

Once the aerosol device 76 is complete, it can be filled through thevalve ready for use. It should be noted that, although the assembly ofparts of the aerosol device 76 is shown in the drawings with the valvepositioned at the top, in use it is likely that the aerosol device willbe inverted from this position. In this regard, it is significant thatone side of the flange, disc 8 will provide a flat base for the insideof the aerosol device. Referring back to FIG. 1, the flat flange dischas, on one side, a raised portion 10 with two slot shaped apertures 12therein. The slots 12 run flat along the face of the flange 8 into theinterior of the valve body 2. Given that the face of the flange 8 willform a flat base of the aerosol device 76 when in use, the positioningof the slots 12 allows for all of the contents of the aerosol device 76to be exhausted. There is nowhere in the device for a substance to‘pool’ and not be in communication with an aperture.

Once the substance passes through the slots 12 in the valve body 2, itthen moves into contact with the valve chamber 16. Because of theseating of the valve stem 32 in the opening 28 of the valve chamber 16,the substance is able to pass through the gaps between the radiallyextending fins 38 of the valve stem 32 and through the opening 28 in thevalve chamber 16. A small amount of the substance is, therefore, presentin the clearance volume between the exterior of the valve stem 32 andthe interior of the valve chamber 16. This constitutes a single ‘dose’to be exhausted from the aerosol device 76. The substance is preventedfrom leaving the clearance volume by the seat gasket 56, which seals notonly the end of the bore 30 of the valve chamber 16, but also the smallaperture 42 in the side of the valve stem 32.

When the valve stem 32 is subjected to an external force, it is pushedinto the remainder of the valve assembly 60 against the force of spring54. As the hollow part of the valve stem 32 passes through the opening28 in the valve chamber 16, the valve chamber 16 is sealed off from thevalve body 2 and, therefore, from the container 66. The movement of thevalve stem 32 also causes the aperture 42 in the side of the valve stemto be uncovered, since the seat gasket 56 remains in place due to theinteraction of its larger diameter part 64 with the flat surface 22 ofthe flange 20 of the valve chamber 16, as the valve stem 32 isdepressed. This allows the substance contained in the clearance volumebetween the valve stem 32 and the valve chamber 16 to enter the hollowpart of the valve stem through aperture 42, and be expelled through theopen end 34 of the valve stem 32 in the form of a fine mist or spray.

The invention consists of a number of distinct features which are, forthe sake of brevity, described in the context of one preferredembodiment. It should be appreciated that the various features areadvantageous in their own right and may be provided separately or in asuitable alternative combination.

The material for making the valve may be at least one selected from agroup of materials consisting of metals; glass; thermoplastics materialsincluding but not limiting to polymers such as PET, polycarbonates,polysulphones and the like and any combinations thereof. Alternatively,the valve assembly may be made of acetyl or polyester, Hytrel®, or thelike.

The elastomeric materials used in the valve assembly may be at least oneof nitrile, butyl, chloroprene, EPDM, TPE, HNBR, POE, chlorobutyl, andbromobutyl or any other thermoplastic elastomer.

The various component parts of the valve assembly may be made by anyappropriate manufacturing techniques. In the case of parts made of aplastics material, molding techniques including, but not limited to,injection molding, two stage blow molding, compression molding, transfermolding, extrusion molding, blow molding, rotational molding orthermoforming are preferred.

If the container used with the valve assembly is formed of an at leastpartially transparent plastics material, e.g. a polysulphone, a user canreadily see how much substance is in the container at any given time.

The invention claimed is:
 1. A valve assembly for an aerosol device, thevalve assembly, in use, being receivable in an opening provided in acontainer of the aerosol device to close said opening, the valveassembly comprising: means on an outside of the valve assembly orproviding a seal with the container when positioned in the openingthereof; a flat portion which, in use, faces towards the interior of thecontainer and provides a flat base for an interior of the aerosoldevice; channels immediately adjacent the flat portion which provideaccess to an interior of the valve assembly; wherein component parts ofthe valve assembly comprise a valve stem, a spring and a valve chamber,and are arranged in a valve body contained therein by a sealing piece toprovide a self-contained valve assembly; and wherein the valve stem andthe valve chamber define a space therebetween that contains one dose tobe released when the valve assembly is actuated.
 2. The valve assemblyaccording to claim 1, wherein a part of the valve assembly iscylindrical.
 3. The valve assembly according to claim 1, wherein saidmeans for providing a seal extends completely around a periphery of thevalve assembly.
 4. The valve assembly according to claim 1, wherein theflat portion is formed by a body part of the valve assembly.
 5. Thevalve assembly according to claim 1, wherein the valve body and thesealing part are snap-fit together.
 6. The valve assembly according toclaim 1, wherein the component parts of the valve assembly comprise aseat gasket positioned between the valve chamber and the sealing piece.7. The valve assembly according to claim 6, wherein the seat gasketsurrounds the valve stem and is capable of sealing an aperture providedin the valve stem.
 8. The valve assembly according to claim 1, whereinthe valve stem is movable within the valve chamber.
 9. The valveassembly according to claim 1, wherein the seal means comprises anelastomeric ring.